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United States · Detailed regional profile

Napa Valley

A small California AVA known especially for Cabernet Sauvignon, with cooler conditions in the south and warmer sites farther north.

Summers are dry and warm, while marine air reaches parts of the valley. Heat, water stress, and harvest timing can all vary by site.

Climate comparisons use the 1991–2020 combined regional record · updated through Aug 20, 2026.

Autumn vineyard rows in Napa Valley, California
Vanessa Sezini / Pexels

Current conditions

Observations through Aug 31, 2026 · 00:30 UTC

Temperature23.7°C
Dew Point12.1°C
Relative Humidity50%
24h Rainfall0.0 mmmodeled IFS total through Aug 29
NWS station average · 2 stations

Temperature, dew point, humidity, and wind are averaged using the same locations and weights as the historical record. The current temperature uses 100% of the configured regional weight.

  • KAPC — Napa, Napa County Airport · 55% regional weight
  • KSTS — Santa Rosa, Santa Rosa Sonoma County Airport · 45% regional weight

NOAA National Weather Service observations. Station readings are point measurements and may not represent every vineyard elevation or exposure.

Vintage explorer

Compare this vintage →

Slightly cooler and slightly drier than normal.

Mean temperature18.3°C
Temperature anomaly-0.2°Cvs 1991-2020
Growing degree days2035base 10°C
Hot days17≥ 35°C

What stood out in 2009

Frost exposure can vary sharply from one site to the next.

Spring frost recorded · Low confidence

The regional record had 1 spring day(s) at or below 0°C.

Frost exposure can vary sharply from one site to the next.

How unusual was 2009?

The ranking compares vintages that meet the data-coverage threshold and use the same source, regional rules, and 1991-2020 baseline.

Growing-season temperature

14th coolest of 35 vintages Cooler than 21 of 34 other vintages 18.3°C

Growing-season rainfall

17th wettest of 35 vintages Wetter than 18 of 34 other vintages 204.6 mm

Heat accumulation

12th lowest of 35 vintages Lower than 23 of 34 other vintages 2036 GDD

Hot days

7th most of 35 vintages More than 25 of 34 other vintages 17 days

2009 month by month

Compared with 1991–2020

Follow heat accumulation, rainfall, frost exposure, and the region’s growing and harvest windows in calendar order.

Frost watch Growing season Harvest window
  1. 1–31
    Frost watchGrowing season

    Heat accumulation

    2009 65 GDD
    Typical 83 GDD

    Rainfall

    2009 70.3 mm
    Typical 111.5 mm
    2009 freezing days
    1
    Typical
    0.2

    Drier than the typical month.

  2. 1–30
    Frost watchGrowing season

    Heat accumulation

    2009 124 GDD
    Typical 131 GDD

    Rainfall

    2009 18.5 mm
    Typical 48.4 mm
    2009 freezing days
    0
    Typical
    0.0

    Drier than the typical month.

  3. 1–31
    Frost watchGrowing season

    Heat accumulation

    2009 250 GDD
    Typical 226 GDD

    Rainfall

    2009 50.6 mm
    Typical 29.5 mm
    2009 freezing days
    0
    Typical
    0.0

    Wetter than the typical month.

  4. 1–30
    Growing season

    Heat accumulation

    2009 279 GDD
    Typical 315 GDD

    Rainfall

    2009 2.1 mm
    Typical 7.4 mm

    Close to the typical monthly pattern.

  5. 1–31
    Growing season

    Heat accumulation

    2009 357 GDD
    Typical 374 GDD

    Rainfall

    2009 0.1 mm
    Typical 0.3 mm

    Close to the typical monthly pattern.

  6. 1–31
    Growing seasonHarvest window

    Heat accumulation

    2009 365 GDD
    Typical 372 GDD

    Rainfall

    2009 0.0 mm
    Typical 1.1 mm

    Close to the typical monthly pattern.

  7. 1–30
    Growing seasonHarvest window

    Heat accumulation

    2009 360 GDD
    Typical 330 GDD

    Rainfall

    2009 2.8 mm
    Typical 2.8 mm

    Close to the typical monthly pattern.

  8. 1–31
    Growing seasonHarvest window

    Heat accumulation

    2009 192 GDD
    Typical 232 GDD

    Rainfall

    2009 111.2 mm
    Typical 37.0 mm

    Wetter than the typical month.

  9. 1–15
    Growing seasonHarvest window

    Heat accumulation

    2009 45 GDD
    Typical 55 GDD

    Rainfall

    2009 6.7 mm
    Typical 30.6 mm

    Drier than the typical month.

View milestone calendar data as a table
Month2009 GDDTypical GDD2009 rainfallTypical rainfall2009 freezing daysTypical freezing days
March 2009 65 GDD 83 GDD 70.3 mm 111.5 mm 10.2
April 2009 124 GDD 131 GDD 18.5 mm 48.4 mm 00.0
May 2009 250 GDD 226 GDD 50.6 mm 29.5 mm 00.0
June 2009 279 GDD 315 GDD 2.1 mm 7.4 mm Outside frost windowOutside frost window
July 2009 357 GDD 374 GDD 0.1 mm 0.3 mm Outside frost windowOutside frost window
August 2009 365 GDD 372 GDD 0.0 mm 1.1 mm Outside frost windowOutside frost window
September 2009 360 GDD 330 GDD 2.8 mm 2.8 mm Outside frost windowOutside frost window
October 2009 192 GDD 232 GDD 111.2 mm 37.0 mm Outside frost windowOutside frost window
November 2009 45 GDD 55 GDD 6.7 mm 30.6 mm Outside frost windowOutside frost window
Calendar data and method

Monthly values are weighted across every configured regional sample using stored Google ARCO ERA5 daily reanalysis. “Typical” is the mean monthly total across 30 baseline seasons. GDD is counted only inside the configured growing window; freezing days are counted only inside the frost-watch window; rainfall covers every displayed calendar day.

Selected-vintage coverage is 100%. Source rows were last retrieved Aug 20, 2026.

Replay the 2009 growing season

246 daily regional observations

Move through the season to follow temperature, rainfall, accumulated heat, and recorded weather events day by day.

Replay data and method

Daily values are weighted across every configured regional sample using stored Google ARCO ERA5 reanalysis. Coverage is 100%. Source rows were last retrieved Aug 20, 2026.

Closest weather matches

These years had the most similar growing-season and harvest weather.

  1. Closest match

    2002

    Most alike in Spring frost exposure and Growing degree days.

    Spring frost exposure
    the same: 0 days
    Growing degree days
    lower: 2 GDD

    Largest difference: Growing-season precipitation — less rain

    View 2002 →

  2. Second closest

    2000

    Most alike in Growing-season precipitation and Growing degree days.

    Growing-season precipitation
    more rain: 2.3 mm
    Growing degree days
    higher: 9 GDD

    Largest difference: Spring frost exposure — fewer frost-exposure days

    View 2000 →

  3. Third closest

    1999

    Most alike in Spring frost exposure and Growing-season precipitation.

    Spring frost exposure
    the same: 0 days
    Growing-season precipitation
    less rain: 2.8 mm

    Largest difference: Harvest precipitation — less rain

    View 1999 →
How similar years are calculated

Method analog-v1-2026-07 standardizes six weather measures across 34 complete ARCO ERA5 comparison years, then measures the distance between them. The calculation runs when the page is requested.

Measures used: Growing-season mean temperature (20%); Growing degree days (15%); Hot-day count (15%); Growing-season precipitation (20%); Harvest precipitation (20%); Spring frost exposure (10%).

Calculated distances: 2002 0.462; 2000 0.715; 1999 0.813.

Growing-season temperature anomalyCompared with 1991-2020
Temperature anomaly by vintage, 1991 to 2026 A line above zero indicates a warmer growing season than the 1991–2020 baseline. Select a point to inspect that vintage. +1.5°C −1.5°C 1991 2000 2010 2020 2026
Growing-season rainfall anomaly
Rainfall anomaly by vintage, 1991 to 2026 Bars show millimeters above or below the 1991–2020 growing-season baseline. Select a bar to inspect that vintage. +200 mm −200 mm 1991 2000 2010 2020 2026
View historical chart data as a table
YearTemperature anomalyRainfall anomalyHot days
1991-0.6°C+13 mm10
1992+0.7°C-19 mm9
1993+0.1°C+14 mm10
1994-0.6°C+33 mm7
1995-0.4°C+21 mm16
1996+0.2°C+11 mm23
1997+0.8°C-27 mm10
1998-1.0°C+87 mm16
1999-0.6°C-7 mm10
2000-0.2°C-2 mm13
2001+0.6°C-65 mm17
2002-0.2°C-59 mm16
2003-0.1°C+57 mm17
2004+0.3°C-28 mm7
2005-0.5°C+111 mm10
2006-0.2°C+136 mm16
2007-0.1°C-71 mm11
2008+0.1°C-93 mm18
2009-0.2°C-4 mm17
2010-1.0°C+82 mm12
2011-1.1°C+193 mm3
2012-0.5°C+50 mm9
2013+0.3°C-125 mm13
2014+0.8°C-64 mm6
2015+0.7°C-101 mm17
2016+0.3°C+14 mm14
2017+0.8°C+6 mm27
2018+0.2°C-30 mm7
2019+0.4°C-31 mm13
2020+0.9°C-104 mm23
2021+0.3°C+90 mm12
2022+0.5°C-55 mm18
2023-0.6°C-29 mm10
2024+0.8°C-65 mm28
2025-0.0°C-32 mm7
2026+0.5°C-88 mm7

winter

9.1°C

-0.4°C vs baseline

355 mm rain · -105 mm

spring

14.7°C

+0.0°C vs baseline

139 mm rain · -50 mm

summer

20.9°C

-0.7°C vs baseline

2 mm rain · -7 mm

harvest

19.0°C

-0.2°C vs baseline

120 mm rain · +49 mm

Weather events

Periods that crossed one of the published regional thresholds, shown in date order.

  1. Spring frost exposure

    Minimum temperature
    -0.1°C
    Duration
    1 day
    Severe-freeze days
    0 days

    The regional model recorded freezing temperatures during spring.

  2. Dry spell

    Duration
    15 days
    Total rain
    0.0 mm
    Daily cutoff
    1.0 mm/day

  3. Dry spell

    Duration
    20 days
    Total rain
    0.3 mm
    Daily cutoff
    1.0 mm/day

  4. Dry spell

    Duration
    28 days
    Total rain
    1.1 mm
    Daily cutoff
    1.0 mm/day

  5. Heat episode

    Peak temperature
    36.0°C
    Duration
    2 days
    Heat accumulation
    30 GDD

  6. Dry spell

    Duration
    101 days
    Total rain
    0.7 mm
    Daily cutoff
    1.0 mm/day

  7. Heat episode

    Peak temperature
    38.1°C
    Duration
    2 days
    Heat accumulation
    33 GDD

  8. Heat episode

    Peak temperature
    36.7°C
    Duration
    3 days
    Heat accumulation
    46 GDD

  9. Heat episode

    Peak temperature
    37.4°C
    Duration
    2 days
    Heat accumulation
    34 GDD

  10. Dry spell

    Duration
    28 days
    Total rain
    0.4 mm
    Daily cutoff
    1.0 mm/day

  11. Heat episode

    Peak temperature
    37.8°C
    Duration
    2 days
    Heat accumulation
    32 GDD

  12. Concentrated harvest rain

    Total rain
    99.8 mm
    Highest 3-day total
    99.4 mm
    Trigger threshold
    20.0 mm

    A large share of the season's rain fell during the harvest period.

  13. Dry spell

    Duration
    16 days
    Total rain
    0.8 mm
    Daily cutoff
    1.0 mm/day
How events are detected

Weather & Vines combined regional series; method event-timeline-v2-2026-07, rules napa-v2-2026-07. Source last updated Aug 1, 2026, calculated Aug 29, 2026. Each configured point must have at least 95.0% coverage.

1991–present

Climate change

Measured regional trends are shown separately from model projections. The observed record ends at the latest complete growing season shared by every published region.

Compare regions

Observed record

Historical trends, 1991–2025

Growing degree days changed +42.2 GDD per decade. The 95% interval is +10.8 to +73.7 GDD per decade, based on 35 eligible vintages.

How it is measured: Across the March 15–November 15 growing season, each day's mean temperature above 10°C adds to the total; cooler days add zero.

Growing degree days · annual change from the 1991–2020 average1991–2025

Scroll horizontally to inspect the full timeline.

View annual growing degree days data
VintageGrowing degree daysChange from 1991–2020
19911962 GDD-124 GDD
19922259 GDD+173 GDD
19932089 GDD+3 GDD
19941945 GDD-141 GDD
19951988 GDD-98 GDD
19962140 GDD+54 GDD
19972272 GDD+186 GDD
19981848 GDD-238 GDD
19991942 GDD-144 GDD
20002044 GDD-42 GDD
20012231 GDD+145 GDD
20022034 GDD-52 GDD
20032080 GDD-6 GDD
20042144 GDD+58 GDD
20051952 GDD-134 GDD
20062037 GDD-49 GDD
20072064 GDD-22 GDD
20082116 GDD+30 GDD
20092036 GDD-50 GDD
20101842 GDD-244 GDD
20111824 GDD-262 GDD
20121976 GDD-110 GDD
20132141 GDD+55 GDD
20142278 GDD+192 GDD
20152252 GDD+166 GDD
20162139 GDD+53 GDD
20172281 GDD+195 GDD
20182156 GDD+70 GDD
20192184 GDD+98 GDD
20202325 GDD+239 GDD
20212151 GDD+65 GDD
20222212 GDD+126 GDD
20231966 GDD-120 GDD
20242292 GDD+206 GDD
20252077 GDD-9 GDD
Growing-season mean temperature
+0.17 °C per decade 95% interval +0.04 to +0.30
Growing degree days
+42.21 GDD per decade 95% interval +10.75 to +73.68
Growing-season precipitation
-15.39 mm per decade 95% interval -26.01 to -4.76
Hot days
+1.02 days per decade 95% interval -0.30 to +2.34
Spring frost days
+0.03 days per decade 95% interval -0.07 to +0.14
Longest dry spell
+7.97 days per decade 95% interval -1.34 to +17.29

Last Updated August 20, 2026

Model ensemble

Projected climate through 2075

Temperature changes are relative to each model’s 1991–2020 baseline. The table combines all three pathways, weighted 70% to SSP2-4.5 and 15% each to SSP1-2.6 and SSP3-7.0.

Scroll horizontally to compare all columns.

PeriodWeighted medianWeighted central 80%Models per pathway
2021-2040+0.9°C+0.5 to +1.3°C25
2041-2060+1.3°C+1.0 to +2.1°C25
2061-2075+1.8°C+1.4 to +2.7°C25
How pathways are combined

For each period and percentile, Weather & Vines takes 70% of the SSP2-4.5 value, 15% of the SSP1-2.6 value, and 15% of the SSP3-7.0 value. Each pathway contains the same 25 models. The weights are an editorial view of the current trajectory, not scenario probabilities.

Last Updated June 29, 2025

Compare projection measures across regions

Typical year · 1991–2020

When to visit

This calendar describes typical regional weather under the selected climate baseline. It is not a forecast for a future trip, and it does not account for crowds, lodging, events, or vineyard access.

Deterministic IFS forecast

Next ten days

Detailed forecast outlook

ECMWF IFS 0.25° via Herbie · model run Aug 30, 2026 at 00:00 UTC · retrieved Aug 30, 2026 at 08:22 UTC

Scroll horizontally to see all forecast dates.

DateSunMonTueWedThuFriSatSunMonTue
High 29°C 23°C 20°C 21°C 24°C 26°C 26°C 29°C 26°C 26°C
Low 12°C 12°C 12°C 12°C 12°C 14°C 12°C 12°C 17°C 19°C
Rain 0.0 mm 0.0 mm 0.1 mm 0.0 mm 0.0 mm 0.0 mm 0.0 mm 0.0 mm 0.5 mm 0.8 mm

Across the typical year: Late July has the warmest median afternoon high (30.7°C); Late December has the coolest (13.0°C). Wet days are most frequent in Late February (42%) and least frequent in Early July (0%). Ties are resolved by calendar order.

Typical afternoon highs and overnight lowsMedians and middle 50% of daily readings

Afternoon highOvernight lowMiddle 50%

Scroll horizontally to inspect all 24 half-month periods.

Typical afternoon highs and overnight lows for Napa Valley Median daily maximum and minimum temperatures for 24 early and late-month periods under the 1991–2020 baseline. Neutral bands show the 25th to 75th percentile. 0°C10°C20°C30°C JanFebMarAprMayJunJulAugSepOctNovDec
How often a day is wetShare of days with at least 1 mm of rain

Scroll horizontally to inspect all 24 half-month periods.

Wet-day frequency through the typical year for Napa Valley The fraction of days receiving at least one millimeter of rain in each early and late-month period under the 1991–2020 baseline. 0%25%50%75%100% JanFebMarAprMayJunJulAugSepOctNovDec
View all 24 periods as a table

Scroll horizontally to view all columns.

Napa Valley typical weather by half-month, 1991–2020
PeriodAfternoon high, median (middle 50%)Overnight low, median (middle 50%)Wet-day frequencyPeriod rain, median (middle 50%)
Jan 1–1513.3°C (11.4–15.3°C)4.0°C (2.1–6.2°C)36%49.2 mm (8.9–99.9 mm)
Jan 16–3114.0°C (12.4–16.6°C)4.5°C (2.6–6.8°C)40%48.6 mm (18.5–130.2 mm)
Feb 1–1515.4°C (13.6–18.3°C)5.2°C (3.2–7.5°C)35%55.3 mm (15.1–107.5 mm)
Feb 16–2915.1°C (12.6–18.8°C)5.4°C (3.3–7.1°C)42%70.1 mm (26.7–130.9 mm)
Mar 1–1517.4°C (14.3–20.7°C)6.0°C (4.0–8.1°C)36%53.1 mm (13.9–79.5 mm)
Mar 16–3118.4°C (15.5–22.2°C)6.8°C (4.8–8.5°C)33%24.2 mm (11.6–71.7 mm)
Apr 1–1519.4°C (16.4–22.4°C)6.7°C (4.9–8.5°C)27%24.8 mm (10.5–55.7 mm)
Apr 16–3021.9°C (19.0–26.0°C)8.3°C (6.5–10.0°C)18%13.0 mm (6.1–23.4 mm)
May 1–1523.8°C (20.4–26.8°C)9.3°C (7.8–10.9°C)14%4.2 mm (0.7–21.7 mm)
May 16–3125.0°C (21.9–28.5°C)10.3°C (9.0–11.9°C)13%3.1 mm (0.4–25.7 mm)
Jun 1–1527.5°C (24.7–30.7°C)11.7°C (10.3–13.3°C)6%0.7 mm (0.0–3.2 mm)
Jun 16–3029.5°C (27.0–32.4°C)12.5°C (11.2–14.1°C)3%0.0 mm (0.0–0.8 mm)
Jul 1–1530.3°C (28.4–32.6°C)13.0°C (12.0–14.3°C)0%0.0 mm (0.0–0.0 mm)
Jul 16–3130.7°C (28.2–32.7°C)13.5°C (12.3–14.7°C)0%0.0 mm (0.0–0.1 mm)
Aug 1–1530.5°C (28.1–33.1°C)13.2°C (12.2–14.6°C)0%0.0 mm (0.0–0.1 mm)
Aug 16–3130.0°C (28.1–32.8°C)13.1°C (12.1–14.2°C)1%0.0 mm (0.0–0.1 mm)
Sep 1–1529.5°C (27.3–32.5°C)12.5°C (11.4–14.1°C)2%0.0 mm (0.0–0.3 mm)
Sep 16–3029.0°C (26.2–31.8°C)12.1°C (10.9–13.4°C)4%0.2 mm (0.0–1.6 mm)
Oct 1–1526.2°C (23.1–29.3°C)10.7°C (9.1–12.3°C)9%2.2 mm (0.0–17.9 mm)
Oct 16–3123.4°C (20.6–26.6°C)9.6°C (7.9–11.0°C)16%11.6 mm (0.4–34.3 mm)
Nov 1–1519.2°C (16.6–22.6°C)7.4°C (5.5–9.2°C)21%20.6 mm (6.5–46.7 mm)
Nov 16–3016.2°C (14.1–18.3°C)5.5°C (3.7–7.8°C)30%29.7 mm (20.8–58.0 mm)
Dec 1–1514.1°C (12.7–15.9°C)4.4°C (2.4–7.5°C)42%68.3 mm (22.1–123.0 mm)
Dec 16–3113.0°C (11.4–15.1°C)3.5°C (1.8–5.5°C)35%53.8 mm (9.9–127.5 mm)

Each year contributes to temperature or rain separately when at least 90% of that period’s days are present. A value is shown only when at least 80% of the baseline years qualify. February 29 is included in late February.

Historical climatology Last Updated August 20, 2026

Season to date

Growing season heat and rainfall

Mar 15–Aug 29, 2026

Growing degree days1455.9base 10°C
Growing-season rainfall120.8 mmweighted regional total
Cumulative growing degree daysBase 10°C

2026 season1991–2020 average

Growing degree days accumulated during the 2026 growing season The solid line accumulates daily mean temperature above 10 degrees Celsius from the configured growing-season start. The dashed line shows the 1991–2020 daily climatological average. 1456 GDD 0 Mar ’26AprMayJunJulAug
Cumulative growing-season rainfallRegional weighted mean

2026 season1991–2020 average

Rainfall accumulated during the 2026 growing season The solid line accumulates daily rainfall in millimeters from the configured growing-season start. The dashed line shows the 1991–2020 daily climatological average. 138 mm 0 Mar ’26AprMayJunJulAug
View growing-season accumulation data
DateSeason GDD1991–2020 average GDDSeason rainfall1991–2020 average rainfall
2026-03-158.83.20.0 mm4.1 mm
2026-03-1619.16.60.0 mm7.4 mm
2026-03-1729.910.10.0 mm9.8 mm
2026-03-1840.713.60.0 mm11.3 mm
2026-03-1951.917.00.0 mm13.5 mm
2026-03-2063.920.10.0 mm18.1 mm
2026-03-2175.023.00.0 mm21.1 mm
2026-03-2283.625.60.0 mm25.8 mm
2026-03-2391.528.00.0 mm30.4 mm
2026-03-2499.530.10.0 mm35.6 mm
2026-03-25106.432.20.0 mm39.8 mm
2026-03-26113.434.40.0 mm42.2 mm
2026-03-27121.937.00.0 mm44.7 mm
2026-03-28129.940.20.0 mm46.4 mm
2026-03-29139.443.80.0 mm48.1 mm
2026-03-30147.547.60.0 mm48.8 mm
2026-03-31152.551.46.2 mm51.7 mm
2026-04-01154.955.29.9 mm54.7 mm
2026-04-02156.059.112.7 mm56.0 mm
2026-04-03160.762.412.7 mm57.5 mm
2026-04-04166.965.412.7 mm60.3 mm
2026-04-05174.468.312.7 mm62.2 mm
2026-04-06180.771.412.7 mm64.6 mm
2026-04-07186.274.612.7 mm67.9 mm
2026-04-08193.177.412.8 mm70.3 mm
2026-04-09199.480.412.9 mm71.5 mm
2026-04-10203.984.124.5 mm72.7 mm
2026-04-11205.287.741.3 mm76.1 mm
2026-04-12205.591.555.3 mm80.8 mm
2026-04-13206.495.357.0 mm83.1 mm
2026-04-14208.099.157.0 mm83.6 mm
2026-04-15209.9102.357.0 mm84.4 mm
2026-04-16213.0106.157.0 mm86.2 mm
2026-04-17218.0110.457.0 mm88.3 mm
2026-04-18222.7114.757.0 mm89.2 mm
2026-04-19227.6119.457.0 mm89.9 mm
2026-04-20229.9124.467.3 mm91.2 mm
2026-04-21231.4129.491.2 mm91.9 mm
2026-04-22232.8134.899.6 mm93.1 mm
2026-04-23235.8140.199.6 mm94.4 mm
2026-04-24239.5145.699.6 mm95.5 mm
2026-04-25241.2151.099.6 mm97.1 mm
2026-04-26242.6156.899.7 mm97.6 mm
2026-04-27244.8162.8100.1 mm98.2 mm
2026-04-28248.1168.9100.1 mm99.2 mm
2026-04-29253.6175.4100.1 mm99.9 mm
2026-04-30260.4182.2100.1 mm100.1 mm
2026-05-01267.3189.2100.1 mm101.6 mm
2026-05-02272.2196.1100.1 mm102.6 mm
2026-05-03276.0202.6100.1 mm103.9 mm
2026-05-04278.1208.9102.1 mm104.7 mm
2026-05-05281.2215.1110.0 mm105.8 mm
2026-05-06287.4221.3110.0 mm106.3 mm
2026-05-07294.4228.0110.0 mm107.5 mm
2026-05-08301.7234.9110.0 mm108.4 mm
2026-05-09310.6241.5110.0 mm109.2 mm
2026-05-10319.3248.3110.0 mm109.7 mm
2026-05-11329.9255.1110.0 mm110.0 mm
2026-05-12338.8261.8110.0 mm110.9 mm
2026-05-13346.7268.4110.0 mm111.4 mm
2026-05-14355.4275.3110.0 mm112.0 mm
2026-05-15365.2282.6110.0 mm114.3 mm
2026-05-16373.8289.8110.0 mm116.4 mm
2026-05-17380.9297.1110.0 mm117.8 mm
2026-05-18390.6304.5110.0 mm120.3 mm
2026-05-19401.4311.8110.0 mm121.6 mm
2026-05-20412.4319.0110.0 mm122.2 mm
2026-05-21423.8326.6110.0 mm123.4 mm
2026-05-22432.5334.4110.0 mm123.6 mm
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2026-05-24445.5350.5110.0 mm124.6 mm
2026-05-25449.8358.2110.0 mm125.3 mm
2026-05-26454.4365.5110.7 mm125.9 mm
2026-05-27458.6373.2112.6 mm126.9 mm
2026-05-28463.6381.3119.4 mm127.9 mm
2026-05-29469.4389.9120.2 mm128.8 mm
2026-05-30476.1398.6120.2 mm129.1 mm
2026-05-31485.2408.0120.2 mm129.6 mm
2026-06-01496.1417.8120.2 mm129.8 mm
2026-06-02506.3427.4120.2 mm129.9 mm
2026-06-03517.5436.9120.2 mm130.2 mm
2026-06-04529.5446.2120.2 mm131.9 mm
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2026-06-08569.7482.7120.4 mm132.9 mm
2026-06-09579.6492.7120.4 mm133.0 mm
2026-06-10594.5502.6120.4 mm133.1 mm
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2026-06-16674.0565.4120.4 mm134.3 mm
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2026-06-18691.7587.2120.4 mm134.6 mm
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2026-06-24744.1654.5120.4 mm134.7 mm
2026-06-25753.2665.7120.4 mm135.1 mm
2026-06-26762.5676.9120.5 mm135.2 mm
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2026-06-28780.9699.7120.5 mm136.3 mm
2026-06-29791.4711.2120.5 mm136.9 mm
2026-06-30801.7723.3120.5 mm137.1 mm
2026-07-01810.9735.4120.5 mm137.1 mm
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2026-08-131338.61254.0120.7 mm137.5 mm
2026-08-141347.51266.6120.7 mm137.5 mm
2026-08-151357.21279.0120.7 mm137.5 mm
2026-08-161368.51291.8120.7 mm137.5 mm
2026-08-171380.71304.1120.7 mm137.6 mm
2026-08-181393.31316.0120.7 mm137.6 mm
2026-08-191406.01327.4120.7 mm137.6 mm
2026-08-201417.51338.4120.7 mm138.1 mm
2026-08-211429.41349.9120.8 mm138.1 mm
2026-08-221442.01361.6120.8 mm138.3 mm
2026-08-231455.91373.4120.8 mm138.3 mm

Forecast outlook

ECMWF IFS 0.25° via Herbie · run Aug 30, 2026 at 00:00 UTC

10-day totals compared with the 1991–2020 combined regional record

GDD accumulation
87 GDDvs 119 GDD average
Total rainfall
1.5 mmvs 0.2 mm average

No unusually hot or wet period stands out in the short-range forecast.

Sun8/30 29°Cavg 30°C 12°Cavg 13°C +10 GDD 0.0 mm
Mon8/31 23°Cavg 30°C 12°Cavg 13°C +6 GDD 0.0 mm
Tue9/1 20°Cavg 31°C 12°Cavg 13°C +5 GDD 0.1 mm
Wed9/2 21°Cavg 31°C 12°Cavg 13°C +6 GDD 0.0 mm
Thu9/3 24°Cavg 31°C 12°Cavg 13°C +7 GDD 0.0 mm
Fri9/4 26°Cavg 30°C 14°Cavg 13°C +8 GDD 0.0 mm
Sat9/5 26°Cavg 31°C 12°Cavg 13°C +9 GDD 0.0 mm
Sun9/6 29°Cavg 31°C 12°Cavg 13°C +12 GDD 0.0 mm
Mon9/7 26°Cavg 31°C 17°Cavg 13°C +12 GDD 0.5 mm
Tue9/8 26°Cavg 30°C 19°Cavg 13°C +12 GDD 0.8 mm

Data and methods

Show data sources and model assumptions

Current temperature, dew point, humidity, and wind use geographically weighted NWS station observations. The 24-hour rain total and 10-day outlook use the 00 UTC deterministic ECMWF IFS 0.25° public forecast retrieved directly with Herbie. Historical temperature and rain combine qualifying GHCN-D stations with ERA5 by geographic area; a missing station day uses the nearest ERA5 value for that station's area. Climate comparisons use 1991–2020.

Forecast comparisons use the 1991–2020 combined regional daily record. Daily high and low averages use the matching date; rainfall and GDD sum the same calendar dates as the forecast period.

This service is based on data and products of the European Centre for Medium-Range Weather Forecasts (ECMWF). Weather & Vines subsets, converts, and regionally weights the forecast fields. ECMWF data are published under CC BY 4.0. ECMWF accepts no liability for errors, omissions, availability, loss, or damage arising from their use.

Climate projections use NASA NEX-GDDP-CMIP6 v2.0, accessed August 23, 2026, with 25 models. Weather & Vines subsets and aggregates the source fields. Source files and derived projection data are under CC BY-SA 4.0; the full roster and limitations are listed in the climate atlas methods.

The Napa Valley model uses a March 15–November 15 growing season, base 10°C GDD, and an operational hot-day marker of 35°C.

The historical series uses 4 ERA5 locations, 13 temperature stations, and 12 rain stations. Interpretation confidence: high. Geometry confidence: authoritative. Rules: napa-v2-2026-07.